legacy/IcingaObject: Render groups only when it is a stored object

This broke activity log.

library/Director/Objects/IcingaObject.php

@@ -2152,7 +2152,7 @@ abstract class IcingaObject extends DbObject implements IcingaConfigRenderer
      */
     protected function renderLegacyGroups()
     {
-        if ($this->supportsGroups()) {
+        if ($this->supportsGroups() && $this->hasBeenLoadedFromDb()) {
             $applied = array();
             if ($this instanceof IcingaHost) {
                 $applied = $this->getAppliedGroups();